In the actual script, the first usage of "the shape" is used to describe the mask Myers wears...

"Darkness, with a small shape in the center of the screen. As MAIN TITLES CONTINUE OVER, CAMERA SLOWLY MOVES IN on the shape.

We get closer and closer until we see that the shape is a Halloween mask. It is a large, full-head platex rubber mask, not a monster or ghoul, but the pale, neutral features of a man weirdly distorted by the rubber. ."